Function regions | Easel.sh

Where Easel Functions run today, how that relates to the CDN, and how to read execution region on requests.

Easel Functions run in a single compute region: US East (iad / us-east-1).

The CDN can still serve cached and static responses from edge locations near visitors. Dynamic requests that need application code run in US East.

Delivery network and compute

Easel’s delivery network and function compute are related but distinct.

A visitor can enter the CDN near their location while the application function runs in US East.

Cached responses and static assets may complete without invoking a function.

Available region

Region	Identifier	Location
US East	`iad`	Northern Virginia, United States

Use iad as the public region identifier in diagnostics and application code that reads platform headers.

Additional function regions are not available yet.

Latency and databases

Place databases and other stateful dependencies close to US East when request-driven work depends on them.

Example:

User in London
    ↓
Easel CDN (near the user)
    ↓
Function in US East (iad)
    ↓
Database in US East

Colocating the function and database usually matters more than placing compute near the user when every request queries a single primary database.

Reduce round trips through:

Query batching
Joins
Transactions
Connection pooling
Runtime Cache
CDN response caching

Reading the region on requests

Easel attaches the function region on the request your application code receives:

X-Easel-Function-Region: iad

Read it from the framework request API or raw headers:

export async function GET(request: Request) {
  const region = request.headers.get("x-easel-function-region");

  return Response.json({ region });
}

Treat this as platform metadata on the request, not as a value you set from the client. Client-supplied X-Easel-Function-Region values do not control routing.

See Request and response headers.

Sessions and local state

Do not store sessions only in local function memory.

Use:

Signed stateless cookies
A shared session store
A database
Another durable authentication system

Instances remain ephemeral and independently scalable even within one region.

Caching before compute

CDN caching can reduce the impact of function-region distance for cacheable routes.

A cached response can be served without invoking the function.

Use CDN caching for:

Public pages
Product catalogs
Documentation
Public API responses
Generated content that tolerates controlled staleness

Use the Runtime Cache to reduce repeated application-data work within functions.

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